Field of the Invention
The disclosure relates to a touch-sensitive device, more particularly to a capacitive touch-sensitive device and a method for making the same.
Related Art of Invention
Recently, with the development of touch-sensitive technology, touch-sensitive devices are widely adopted in various electronic products, such as mobile phones, personal digital assistants (PDAs), input interface of gaming devices, and touch panels. In practice, the touch-sensitive device is usually combined with a flat panel display (FPD) to form a touch panel to be mounted on various electronic products. A user may input data and instructions through the touch panel instead of conventional input devices such as keyboards and mouses, thereby bringing great convenience to the user.
Normally, a transparent electrically-conductive substrate of the capacitive touch-sensitive device is mainly constituted by a transparent substrate and a patterned transparent electrically-conductive layer. The method for making the aforesaid transparent electrically-conductive substrate is mainly to coating a transparent electrically-conductive layer, which is usually made of transparent metal oxide, such as indium tin oxide (ITO) and the like, onto the non-conductive transparent substrate. Thereafter, the transparent electrically-conductive layer is further subjected to photolithography process and etching to form a transparent electrically-conductive layer which has a predetermined pattern (e.g., to form an electrode pattern of multiple rows or intersecting rows and columns) and serves as the sensor electrode layer of the capacitive touch-sensitive device. The aforesaid electrode pattern includes an ITO zone (i.e., the electrode zone), and an etched zone, on which no ITO conductive layer is formed so that light can be directly transmitted to the transparent substrate. However, since these two zones have different refractive indexes, the user may clearly observe etched lines formed at the junctions between the two, which may seriously and adversely affect the visual appearance of the touch panel.
To solve the above-mentioned problem, skilled artisans in the field tend to adopt index matching (IM) membrane layers. Referring to FIG. 1, a method to reduce significance of brightness of etched lines of a patterned ITO layer mainly includes: depositing an IM membrane layer 12 onto a polyethylene terephthalate (PET) layer 11; depositing an ITO layer 13 onto the IM layer 12; and lastly, patterning the ITO layer 13 to form a patterned ITO layer 14, where the IM membrane layer 12 is usually constituted by a plurality of high refractive index dielectric layers (such as Nb2O5), and a plurality of low refractive index dielectric layers (such as SiO2) alternately stacked with the high refractive index dielectric layers. Although such IM membrane layer 12 may reduce the brightness of the etched lines of the patterned ITO layer, the thickness of the IM membrane layer 12 is comparatively large, resulting in relatively high production cost and a time-consuming manufacturing process. Moreover, the IM membrane layer 12 may be an obstacle with respect to thinning of the touch panel.
From the description above, to lower the brightness of the etched lines of a patterned transparent conductive layer for improving displaying effect of a touch panel and to simultaneously reduce the production cost of and thinning of a capacitive touch-sensitive device have become tasks for the skilled artisan.